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802.1D – Selective Multicast

802.1D – Selective Multicast. Network Protocols and Standards Autumn 2004-2005. GMRP. GARP Multicast Registration Protocol A mechanism that allows:

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802.1D – Selective Multicast

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  1. 802.1D – Selective Multicast Network Protocols and Standards Autumn 2004-2005 CS573: Network Protocols and Standards

  2. GMRP • GARP Multicast Registration Protocol • A mechanism that allows: • End stations to dynamically register (and subsequently de-register) group membership information with the MAC bridges attached to the same LAN segment • Bridges to disseminate that information across all bridges in the bridged LAN that support extended filtering services • Operation of GMRP depends upon the services provided by GARP (Generic Attribute Registration Protocol) CS573: Network Protocols and Standards

  3. Result of Group Membership Information Registration and Propagation • Frames sent to a particular group: • Can be received on all LAN segments to which registered GMRP participants are attached • Bridges filter frames on ports which have not had group registration entries created by GMRP • Multicast frames are not transmitted on those LAN segments which: • Neither have registered GARP participants • Nor are in the path, through active topology, from source to registered members CS573: Network Protocols and Standards

  4. Open Host Group Concept • Any GMRP participants that wish to receive frames transmitted to a particular group or groups register their intention to do so by requesting membership to the concerned group(s) • Any station that wishes to send frames to a particular group can do so from any point of attachment in the extended LAN • MAC service users that are sources of MAC frames for a group do not have to register as group members themselves unless they also wish to receive frames sent to that group by other sources CS573: Network Protocols and Standards

  5. Example of an Active Topology LAN A Bridge FDB Bridge FDB Bridge FDB Bridge FDB LAN B LAN C LAN D Bridge FDB Bridge FDB Bridge FDB Bridge Station CS573: Network Protocols and Standards

  6. Active Topology with Group Members LAN A Bridge FDB Bridge FDB Bridge FDB Bridge FDB M LAN B LAN C LAN D M M Bridge FDB Bridge FDB M Station that is a member of group M M Station that is not a member of group M M CS573: Network Protocols and Standards

  7. Example 1 with Active Topology LAN A Bridge FDB Bridge FDB Bridge FDB Bridge FDB LAN B LAN C LAN D M Bridge FDB Bridge FDB CS573: Network Protocols and Standards

  8. Example 2 with Active Topology LAN A Bridge FDB Bridge FDB Bridge FDB Bridge FDB LAN B LAN C LAN D Bridge FDB Bridge FDB M CS573: Network Protocols and Standards

  9. Example 3 with Active Topology LAN A Bridge FDB Bridge FDB Bridge FDB Bridge FDB LAN B LAN C LAN D M Bridge FDB Bridge FDB M CS573: Network Protocols and Standards

  10. Group Registration Entries in FDBs Resulting in a Directed Graph LAN A Bridge FDB Bridge FDB Bridge FDB Bridge FDB M LAN B LAN C LAN D M M Bridge FDB Bridge FDB M M CS573: Network Protocols and Standards

  11. Source Pruning • Should a station transmit a frame without knowing whether there is a recipient or not? • End stations use group membership information registered via GMRP to keep track of the set of groups for which active members exist • End stations may suppress the transmission of frames for which there are no valid recipients (or active members) • Avoids unnecessary flooding of traffic on the LAN if there are no members that wish to receive such traffic CS573: Network Protocols and Standards

  12. Default Group Filtering Behavior All Groups Unregistered Groups Registered Groups Forward Filter Forward Filter CS573: Network Protocols and Standards

  13. Default Group Filtering Behavior • By default, there are three different group services • Forward All groups • Forward unregistered groups • Filter unregistered groups • Each port may be assigned these default behaviors CS573: Network Protocols and Standards

  14. Use of “Forward All Groups” • Frame is forwarded unless an explicit static filtering entry exists • To ensure that regions of the extended LAN that contain legacy devices can receive all multicast frames • Can use static configuration to explicitly disallow certain multicast traffic • To allow successful operation of devices that require promiscuous reception • Routers • Network Monitors CS573: Network Protocols and Standards

  15. Use of “Forward Unregistered Groups” • Group addresses which do not have dynamic FDB entries are forwarded • Group addresses which have dynamic FDB entries are forwarded or filtered based on the dynamic entry • Useful in circumstances where GMRP-aware devices distinguish between legacy multicast addresses for which they do not register and “new” multicast addresses for which they register • Must ensure that GMRP-aware end stations do not register for legacy multicast addresses CS573: Network Protocols and Standards

  16. Use of “Filter Unregistered Groups” • Group addresses which do not have dynamic FDB entries are filtered • Group addresses which have dynamic FDB entries are forwarded or filtered based on the dynamic entry • Intended for operation with GMRP-aware end stations only CS573: Network Protocols and Standards

  17. Type of Information Registered by GMRP • Group membership information • Indicates that one or more GMRP participants that are members of a particular group (or groups), exist • Carries the group MAC address(es) information associated with the group(s) • Results in the creation or updating of group registration entries in the filtering database to indicate the port(s) on which the members of the group(s) have been registered • Group service requirement information • Indicates that one or more GMRP participants require “forward all groups” or “forward unregistered groups” to be the default group filtering behavior (applied to a frame whose group address is not in the FDB) CS573: Network Protocols and Standards

  18. The Extended FDB • The extended FDB contains information in the form of filtering entries that are either: • Static entries • Explicitly configured by the management • Dynamic entries • Automatically entered into the FDB by the normal operation of the bridge • Group registration entries • Created, modified, and deleted by the operation of GMRP CS573: Network Protocols and Standards

  19. GARP • Objective: • Registration and dissemination of information of any generic attribute over a bridged LAN • End stations can issue/revoke declarations for the attribute values • Attributes are opaque to GARP • It is up to the GARP application to define and interpret the generic attribute • Think of GMRP as an application which uses GARP! CS573: Network Protocols and Standards

  20. GARP Control Messages • Two principal control messages • Join Message • Sent by a user to register an attribute • Leave Message • Sent by a user to de-register an attribute There will be other messages derived from these two principal messages! CS573: Network Protocols and Standards

  21. GARP: Design Principles • Fully distributed protocol • Simple • No explicit information about members • Resilient against loss of a single control packet • A participant that wishes to make a declaration sends two join messages • Scalable • Transmission of GARP control messages by participants is randomized over time • An applicant that sees a join message for the same attribute it intends to register considers it as if it were one of its own CS573: Network Protocols and Standards

  22. GARP: Design Principles • Soft State • No acknowledgments, no confirmation, no information about registered users • Registrations have to be refreshed continuously • Every 10s, the bridge issues a leave all message “threatening” to de-register all groups. Users still interested in keeping the registration alive send Join messages • Resilient to failure of GARP participants • This is in case the GARP participants fail to see some GARP messages such as Join… • Operates in homogeneous and heterogeneous LANs CS573: Network Protocols and Standards

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